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Wednesday, November 23, 2016

Q. I'm getting ready to
place an order for wine grape plants. Currently I have 25 plants that are 3+
years old. These consist of mainly Zinfandels and Cabernets with a few Merlots.
Can you give me any info on nurseries to deal with and type of plants I may
need?

A. You can wait a bit to make a wine grape order unless you tell them not to ship until late February or March. I want to avoid freezes after planting.

Basically stick with the
so-called hot climate grapes. Summer Muscat is a good one for you. Others to
look at include Syrah (Shiraz), Petit Syrah, Barberra, Grenache, Sangiovese, Malbec,
Tempranillo,

Zinfandel growing in Las Vegas in trials 2007-2011

Pinot Noir growing in Las Vegas. Not a grape I would normally recommend here but I wanted it so I grew it and it did surprisingly well

Sauvignion Blanc growing in Las Vegas trials

Alicante Bouschet in veraison growing in Las Vegas trials. Another problem with hot weather is uneven ripening of the grapes due to hot weather and warm nights

Viognier to get you started. Look closely at Malbec if you like
Malbec wines. Syrah is always a good one for blending as well as Barberra, Grenache,
Merlot, Petit Syrah, Zinfandel and Primativo which some claim is a Zinfandel.

Q. I have vegetable
garden. Do I have to cover with a sheet if it freezes?

A. It depends on the
vegetables and the site. Vegetable gardens located in warm areas of the yard
with reflected heat and very little wind are much warmer. They may not need to
be covered or covered less often than those that are exposed. Vegetables
growing in these locations are not as likely to freeze during the winter.

Freeze damage to tomato plant

Freeze damage to tomato fruit

Of course any of the warm season vegetables like
tomatoes, peppers, eggplant, squash, etc. are going to freeze as soon as
temperatures drop below freezing. In fact, they can suffer some damage when
temperatures drop to the temperature of your refrigerator.

Some warm season vegetables like beans may freeze to the
ground at the hint of a freeze while others like peas, spinach and radishes may
sail through the winter with no problems. Sorry that I can't give you a
definite answer on that because there are so many variables.

Bush bean collar rot due to cold soils

To be on the safe side get yourself a 1 ounce or more
frost blanket and cover your growing area when temperatures are predicted to
drop below freezing. Depending on the frost blanket, it can allow 50% or more
of the light to reach the vegetables and it also breathes while it can raise
the temperature under the blanket five or 6° F. It also keeps the wind off of
the vegetables.

Follow the direction and tack it down tightly so the wind
doesn't get under it. Or put some weighted objects along the perimeter of the
blanket. Don't use burlap or plastic sheeting. Spend the money, buy the 1 ounce
or heavier frost blankets and they will last for three or four seasons or more.

Q. I heard the Israelis
established a low desert apple tree. A few orchards have been established in
the Phoenix area. I would like to learn more with the intent to purchase.

A. There are a couple of
apples suitable for the low desert developed in Israel but the quality of the
apple is typically not the best, in my opinion, unless you are a big fan of ‘Yellow
(Golden) Delicious’. Both “Anna’ and “Ein Shemer’ apples were bred in Israel as
a “low chill” apple for warm climates, not necessarily hot desert climates.

Anna grown in Las Vegas, Nevada in the Eastern Mojave Desert

“Low chill” refers to the chilling requirement required
by some fruit trees to flower and produce fruit the next growing season. A
chilling requirement is a specific number of hours below a threshold
temperature, usually around 45° F, so they “recognize” winter has passed.

Just because a fruit tree has a low chilling requirement
does not necessarily mean it produces good fruit in a hot desert climate. Hot
desert climates are not the best places for apples. It doesn’t mean necessarily
that an apple tree won’t grow but may have trouble producing fruit and decent
yields and the flavor, texture and keeping qualities may be inferior. Apple
fruit frequently sunburn in our hot summer climate and develop thick skins and
high sugars but lower acidity. These climates are more suitable for stone fruit
such as apricots and peaches.

Immature apple in the early stages of sunburn

Apple fruit with severe sunburn from lack of protection from late afternoon sun (West)

Hot deserts without cool nights close to harvest don’t
develop a good balance of acids and sugars for flavor development. Cool nights
are important for this. A 4000 foot elevation adds cooler nights which is very
important for flavor development.

The orchards in Arizona that I know of such as those near
Wilcox, Arizona, are at a 4000 foot elevation or higher. Compare that with
Phoenix at an elevation of around 1000 feet. These higher elevations and can
handle some popular apples like Granny Smith, Fuji, Fuji, Gala and Pink Lady.

Q. I have a fruit bearing
plum tree approximately 2 years old. I noticed an amber hard substance on the
trunk. I think it’s borers. If it is, what can I do to save it and still be
able to eat the fruit?

A. The most effective way
to kill borers is to apply a systemic pesticide and let the tree distribute
this pesticide everywhere inside it. There is a very popular systemic
insecticide available nearly 100% effective at killing borers if they are
present.

This insecticide is distributed everywhere (systemic) inside
the tree and lasts for nearly 12 months. And yes, it is labeled for fruit trees
that are bearing fruit as well as vegetables. This pesticide applied to food
bearing crops makes me nervous for obvious reasons.

Let me present to you an idea that does not require
pesticides but a little work on your part. I have observed it to be about 80%
effective. This requires a sharp knife and a method to sanitize it such as
alcohol, butane lighter or even Pine-Sol.

Plum sap from a pruning cut in the spring

Sap oozing from the trunk of a fruit tree due to overwatering

Plums are very sappy trees. Any injury to living parts of
the tree cause sap to be produced. The production of sap is a defense mechanism
against “intruders”. The tree does not differentiate between damage from boring
insects and damage caused by pruning, invading diseases or environmental damage.

Extensive damage to the trunk of plum and bark is peeling from the west side

To a plum tree, it’s all the same. It reacts by producing
sap. If it is an intruding insect like a borer, sap engulfs and frequently
suffocates it. If the damage by boring insects is extensive, loose bark easily
lifts away from the damaged area because that area is dead.

Borer damage under the bark leaving behind "debris" in the tunnels just under the bark from eating

Damage from boring insects most first appears on the west
or south facing sides of the trunk and limbs or on their upper surfaces. A tree
may have damage for one or two seasons before you see parts of it suffering
outwardly. On plums, sap is a good indicator something is going on.

The only way to find out if a boring insect is involved is
to inspect the wood under the sap for damage. It is easiest to do this after
the leaves drop in December. You can wait. It’s cold now and they are not
active.

When you are ready, take a very sharp, sanitized knife
and remove the sap along with the bark just under it. Look for damage to the
trunk or limbs in the exposed wood. Boring insects leave debris from feeding, in
tunnels, just under the bark.

Borer damage removal using a sharp knife removing all the damaged bark to fresh wood

If you do not see damage to the wood under the sap, then
this damage is not due to borers. Leave it alone if the limb appears otherwise
healthy. If you see insect damage in the wood under the bark, cut and remove
ALL bark from the damaged area with your sharp knife and let it heal on its own.
If the damage is extensive and the limb is weak, remove it.

There is no pesticide you can apply to the tree that will
kill the borers AND leave the fruit safe to eat in my opinion even if it’s on
the label and you can use it for that purpose.

Sunday, November 20, 2016

Q. Last November my next
door neighbor’s African sumac trees were pruned to a trunk and branches. They
were cut back so much I was sure they were being removed but was told they
would leaf again. They did and are green and a lovely, smaller shape. I am
planning to take the plunge with my tree but was advised to wait until February
to avoid freezing damage. What should I do?

A. I will get to the
February pruning. There is a right way and wrong way to radically prune large
trees to a much smaller size. African sumac trees will survive this kind of
pruning and you can get a much smaller tree. But the resulting growth from this
tree will be weakly attached to the main trunk and large branches. This results
in a lot of future wind damage to the tree and will cost more money to have
this repaired later.

Radical pruning that dramatically reduces the size of a
tree must always be done during the winter months. Winter freezing damage to
this tree does not happen very often here so I am not overly concerned about
waiting until February. Not a bad idea though if the tree will look ugly until
it regrows.

We are talking about African sumac now. This type of
pruning will not work on all large trees. If this type of pruning had been done
to most ash trees, it would’ve killed them.

The acceptable method for reducing the size of larger trees
is a technique called “drop crotching”. This technique identifies the tallest
limbs and removes them at a “crotch” in the tree, using a clean cut that leaves
no stubs. When cutting trees in this way, the height is reduced but strong
limbs remain to support the canopy and reduces future wind damage.

Basically, “drop crotching” can be done to any large tree,
not just African sumac. The type of pruning you saw done to your neighbor’s
trees only works on trees that sucker easily from larger limbs.

Dramatically reducing the size of trees by pruning is
best left to tree care professionals, certified arborists, who have passed
rigorous exams demonstrating that they understand and can practice highly
specialized form of pruning correctly. They are more expensive but they know
how to do it correctly.

Q. Can you please tell me
if it is possible or not to use volcanic rock dust on a Venus fly trap to
promote its growth?

A. Rock dust is a
marketing term which means a very finely ground powder from different sources
that contains dozens of minerals in small quantities. It is thought that soils
which are used for a very long time become depleted of some minerals that
cannot be replaced with fertilizers. Recently, this term has become a hot topic
among gardeners in the social media like YouTube and some gardening internet
blogs.

I became interested in it because I was getting questions
regarding its use. I experimented with three different kinds of rock dust and
compared them for one growing season in some raised vegetable beds. All of the
raised beds were composted, as they would be, normally, at the start of a
growing season.

Perhaps it promotes growth in soils that do not have
enough nutrients but I did not test that. I have not seen any advantages to
vegetable growth when it is applied to raised beds and the soil has been
composted and amended correctly.

It does not hurt anything to apply it in small quantities
and it can be inexpensive insurance if you want to be sure. You don’t need
much.

Venus flytrap in nature grows on very poor soils. It gets
its nutrients primarily from the soil when it can get it. Alternatively, they
also take nutrients from small insects that walk or fly into their trap. They
evolved this way because of the poor soils. But catching insects and devouring
them is an alternative to getting nutrients from the soil or leaves.

Regardless, the soil must drain well when growing these
plants. Lava rock, perlite or pumice will help in that regard. They like high
humidity so growing them in an enclosed terrarium will help. Adding rock dust
to the soil will not hurt it. But help it? Perhaps if the soil is lacking in
any of the plant nutrients found in the rock dust.

Personally, I would use liquid fertilizer sprayed on the
foliage much like you would orchids. This plant would like very much compost
tea applied this way. They do not like rich, wet soils.

Welcome to Xtremehorticulture

Home. My home base is Las Vegas, Nevada, in the Eastern Mojave Desert. This blog focuses on horticulture in Deserts.

Me. Desert Horticulture is very different from horticulture in wet climates. Very few people talk about it. This blog focuses on it. My experience in horticulture span over 50 years; time as an applied academic and now working as a consultant. This blog shares my experience and advice in Desert Horticulture. Work in Northern, East and Southern Africa, Western and Central Asia and the Middle East have expanded my views on Desert Horticulture.

Questions. I reply to questions sent to me as quickly as possible. Please include pictures. It helps. Unless questions are confidential, I post them on this blog if they add new information.